This invention relates to a method of manufacturing a diaphragm backing plate for use in a brake booster.
The manufacture of a backing plate is usually achieved through a progressive stamping procedure that includes moving a coil of metal to a first station where a rough blanked disc having a first diameter in stamped or punched out of the coil. The rough blanked disc is then moved to a second station where the first diameter is then reduced by a secondary trim operation to a desired second diameter that is approximately equal to a desired diameter for a backing plate plus a width for a lip that will be rolled on the peripheral edge. The trimmed disc is then transferred to a third station where the lip is rolled around the peripheral edge to define a desire diameter for the backing plate. This process while functioning in a satisfactory manner includes waste as material is lost as scrap because of a need for the secondary trim operation blanking step. While the amount of material loss for an individual plate may not be excessive, the cumulative loss for a coil of metal may amount to up to one percent of the roll of metal.